1. Field of the Invention
The present invention relates generally to a method of controlling a plurality of active suspensions for an automotive vehicle. More particularly, the present invention relates to a method of controlling the active suspensions, wherein a plurality of correction logics are provided in a control system including a longitudinal acceleration sensor and a lateral acceleration sensor.
2. Description of the Related Art
A conventional control system of active suspensions for an automotive vehicle using pneumatic springs includes a vertical acceleration sensor, a suspension stroke sensor, a controller and a flow rate control valve. The vertical acceleration sensor detects a vertical acceleration above the spring for each of front/left, front/right, rear/left and rear/right air suspensions. The suspension stroke sensor detects a vertical relative displacement quantity above and below the spring for each air suspension. The controller calculates an instruction air flow quantity to be fed to and discharged from each air suspension based on the vertical acceleration above the spring detected by the vertical acceleration sensor, on the vertical relative displacement quantity detected by the suspension stroke sensor and on a vertical relative displacement speed obtained from the vertical relative displacement quantity by calculation. The flow rate control valve performs air feeding or air discharging in accordance with the instruction flow quantities independently for each air suspension. With the conventional active suspensions, each air suspension is controlled independently so as to vary an apparent mass of the vehicle body and damping and spring effecta. The above-described control system of the active suspensions have been developed by the same applicant of the present patent application and it was already laid open under Japanese Laid-Open Patent NO. 139,709/1987.
The conventional active suspensions are controlled by feeding and/or discharging air in each air suspension according to a vertical acceleration of the mass above the spring, and a relative displacement and a relative displacement speed between the masses above and below the spring. Thus, it is very effective for a soft feeling when receiving a sudden upward impulse from a road. Moreover, it is also very effective to keep the vehicle in proper attitude when receiving a slow moving force from the road.
In addition, with respect to the conventional control system of the active suspensions, it has been proposed that the control system is additionally provided with means for detecting a longitudinal acceleration of the vehicle body, means for detecting a lateral acceleration of the vehicle body and a control logic for controlling an attitude of the vehicle body under a transitional condition during acceleration or turning movement of the vehicle based on the longitudinal acceleration and the lateral acceleration.
With respect to rolling caused by centrifugal force during turning movement of the vehicle, it is preferable that a rolling angle is generated in the opposite direction to a steering direction of a conventional vehicle, and it is more natural that a rolling angle is generated in the steering direction of the conventional vehicle. Accordingly, there is existent a problem that the vehicle body maintains a horizontal attitude during turning movement of the vehicle.
The present invention has been made to solve the foregoing problems.